Drill/countersink assembly and method for producing countersunk holes

Abstract

A countersink cutter or drill/countersink combination or similar rotary cutter or assembly for drilling/countersinking or performing similar cutting operation to precise depths in various applications, including aerospace applications, uses a pneumatically driven pistol grip motor attached to a tool assembly or countersink tool assembly. The countersink tool assembly, which has a multi-fluted cutter, is coupled to and is coaxial with the spindle. The cutter can be preset to a precise depth at the back end of assembly through the slot or using gage stops on the guide rods fastened to brackets by setting the gage between gage stops and the bracket.

The invention claimed is: 
     
       1. A countersink or other rotary cutting tool assembly adapted to be attached to a drill motor for drilling and countersinking a hole or doing a similar operation in a workpiece, comprising: an approximately cylindrical rear subassembly extending between a first end and a second opposed end and having a slot for a gage, wherein the outer diameter of the assembly defines an approximate first cylinder, the rear subassembly is mounted to a drill motor with an adaptor sleeve; an approximate first cylindrical body has a through hole for providing access to a chuck for tightening purposes and has two O-ring grooves where two O-rings are mounted on; said rear subassembly also comprises a cylindrical vacuum sleeve that slides over the first cylindrical body with the O-rings mounted on it; an approximate cylinder front assembly having a main body, a coaxial spindle with a spindle shaft, wherein the front subassembly moves laterally in relation to said rear subassembly; the front subassembly also comprises a spring with a bushing inside it entrapped in said main body; having quick change mechanism for removal of a nosepiece subassembly; and said nosepiece connected to external source at the fitting for vacuuming debris; an approximately cylindrical countersink cutter, operably connected to said drill motor, said coaxial spindle having a pin inserted in a bore to accommodate a cutter shaft using a second quick change mechanism to engage, having a body diameter with knurls and a hole through, a pilot and a set of cutting edges, wherein said rear subassembly is stationary; said spindle shaft mounts into said drill motor; said cutter shaft has a flat front end surface or edge and a flat back end along a longitudinal axis, an angular flat surface, and has a groove to accommodate an O-ring; said front end surface or edge of said cutter shaft coincides with a back end of said body diameter of said cutter; said body diameter has said knurls on a cylindrical body diameter surface; an angular flat surface locks into said pin of said coaxial spindle; and an intersection point of the longitudinal axis and said cutting edges, when projected on to the longitudinal axis, is held in alignment at a substantially constant distance from the back end surface of said cutter; and the distance between a front surface of said coaxial spindle and the front surface of said nose piece is constant and is equal to the distance between said front end surface or edge of body diameter flat surface and the center of the radius when drawn between the tangent of said pilot diameter and said cutting edges or the distance between the spindle bore surface and the nose piece front surface are constant and is equal to the distance between the back flat surface and the center of the radius between the tangent of pilot diameter and the cutting edges plus longitudinal distance between said intersection point and said center of the radius; the front subassembly is set at a desired distance from the rear subassembly, locking the front assembly in place with the gage stops; a subassembly consisting of a rear bracket mounted on said stationary first cylindrical body, connected with an alignment rod with screws to a front bracket mounted on said main body; one of a speed controller, a long cylindrical pin or protrusions mounted on said front bracket facing towards said rear bracket adjusted to be used as a stop, said gage is used between said stop and said rear bracket for setting up the depth; a set of gage stops, one each adjustable and fixed respectively mounted on said guide rod, one on each side of said front bracket; a gage stop depth set by using either said gage between said adjustable gage stop and said front bracket and locking said adjustable gage stop and said fixed gage stop against said front bracket, or by moving said gage stops mounted on said guide rod, one on each side of said rear bracket where depth is set by using gage between adjustable gage stop and said rear bracket and locking said gage stops against said rear bracket; with said adjustable gage stop set in correct position, said front subassembly is moved towards said rear subassembly against said adjustable gage stop making said cutter fully exposed for countersinking, said fixed gage stop is secured against said front bracket touching it making the countersink tool ready with said cutter fully exposed to correct depth; keeping said cutter fully exposed is achieved when said guide rods are secured to said front bracket and slide through said rear bracket, said front assembly is pushed towards said rear bracket and said adjustable gage stop is moved to touch said rear bracket and secured to said guide rod and also fixed gage stop moved against rear bracket on outside of said bracket and secured to said guide rod thereby locking the position of said cutter fully exposed. 
     
     
       2. The assembly as claimed in  claim 1 , wherein said angular flat on said cutter shaft and said pin are inserted at an offset position from center through said bore of said coaxial spindle, and engage each other to create said first quick change mechanism for said cutter to be mounted and removed from said coaxial spindle and provide torque to said cutter. 
     
     
       3. The assembly as claimed in  claim 1 , wherein said cutter shaft is one of a threaded cutter shaft design, a quick change cutter mechanism with a slotted shank on said cutter shaft and a pin driver on said spindle, a cutter shaft with indentations to accept balls encased between a sleeve mounted on said spindle body inside diameter and outside diameter, or a cutter shaft with a varying number of flats on the periphery and a groove on said cutter shaft to accept balls that are encased between a sleeve mounted on said spindle body inside diameter and outside diameter and the same number of flats inside said spindle hole to accept said cutter shaft to provide torque. 
     
     
       4. The assembly as claimed in  claim 1 , wherein said nosepiece is a telescopic design where said front bushing is retractable and said spring is loaded and guided by said pin and said slot without hampering vacuum action and preventing said sleeve from turning during drilling action. 
     
     
       5. A method for adjusting a countersink or other rotary cutting tool assembly as claimed in  claim 1 , comprising: adjusting the front end of the cutter shaft to coincide with the back end of diameter of the cutter; locking the angular flat surface into a pin of the spindle; and holding the intersection point of the longitudinal axis and edges, when projected on to the longitudinal axis, in alignment at a substantially constant distance from the back surface of the cutter and equal to spindle bore surface and the nosepiece surface in assembly. 
     
     
       6. The method as claimed in  claim 5 , whereby adjusting said gage between said front subassembly and said rear subassembly, used between said gage stops and said brackets, achieves the depth control required for drilling or countersinking.